Method and apparatus for treating canine cruciate ligament disease

ABSTRACT

Protheses and methods for treating canine cruciate ligament disease are disclosed comprising placement of a specifically configured implant on the femur or tibia to displace targeted muscle or connective tissue associated with the stifle joint so as to reduce cranial tibial thrust.

RELATED APPLICATION

This is application is a continuation of International PatentApplication No. PCT/US2013/058877, filed Sep. 10, 2013, and titled“Method and Apparatus for Treating Canine Cruciate Ligament Disease”,which claims the benefit of priority of U.S. Provisional PatentApplication Ser. No. 61/699,089, filed Sep. 10, 2012, and titled “Methodand Apparatus for Treating Canine Cruciate Ligament Disease”; thisapplication is also a continuation-in-part of U.S. Nonprovisional patentapplication Ser. No. 13/002,829, filed Aug. 27, 2010, and titled “Methodand Apparatus for Force Redistribution in Articular Joints”; whichapplication is a 371 of International Patent Application No.PCT/US10/46996, filed Aug. 27, 2010, and titled “Method and Apparatusfor Force Redistribution in Articular Joints”, which claims the benefitof priority of U.S. Provisional Patent Application Ser. No. 61/237,518,filed Aug. 27, 2009, and U.S. Provisional Patent Application Ser. No.61/288,692, filed Dec. 21, 2009, each entitled “Method and Apparatus forForce Redistribution in Articular Joints.” Each of the foregoingapplications is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to the field of veterinaryorthopedic disease. In particular, the present invention is directed toan interventional technique and an implant for treating canine cruciateligament disease.

BACKGROUND

Cruciate ligament degeneration or rupture is a common canine disease.The cruciate ligaments are the primary stabilizing structures of caninestifle joint. The canine stifle joint is condylar synovial joint. Theprimary motion of joint is flexion and extension. The three majormuscles comprising the caudal thigh group are the biceps femoris, thesemitendinosus and the semimembranosus, also collectively known as thehamstring muscles. The bones, muscles, tendons, ligaments etc. of thecanine stifle joint are shown in detail in FIGS. 1-6 (Reference:Carpenter, D. H. et al, Mini Review of Canine Stifle Joint Anatomy,Anat. Histol. Embryol., 29, 321-329, 2000).

A cranial view of the left stifle showing associated ligaments andstructures is shown in FIG. 1. The following features are identified:1A, femoral trochlea; 2A, lateral ridge of femoral trochlea; 3A, tendonof long digital extensor; 4A, tendon of popliteus; 5A, lateralcollateral ligament; 6A, lateral meniscus; 7A, tibial tuberosity; 8A,patellar ligament; 9A, patella; 10A, parapatellar fibrocartilage; 11A,intermeniscal ligament; 12A, medial meniscus; 13A, medial collateralligament; 14A, cranial cruciate ligament; 15A, caudal cruciate ligament;16A, medial ridge of the trochlea.

A caudal view of the right stifle showing associated ligaments andstructures is shown in FIG. 2. The following features are identified:1B, cranial cruciate ligament; 2B, lateral collateral ligament, 3B,lateral meniscus; 4B, cranial ligament of the fibular head; 5B, caudalligament of the fibular head; 6B, fibula; 7B, caudal meniscotibialligament of the lateral meniscus; 8B, caudal cruciate ligament; 9B,medial meniscus; 10B, medial collateral ligament; 11B, meniscofemoralligament.

A lateral view of the right stifle showing associated ligaments andstructures is shown in FIG. 3. The following features are identified:1C, popliteus tendon; 2C, lateral collateral ligament; 3C, sesamoid; 4C,lateral femoropatellar ligament; 5C, quadriceps muscle group tendon ofinsertion; 6C, patella; 7C, patellar ligament; 8C, lateral meniscus; 9C,tibial tuberosity; 10C, tibial crest; 11C, long digital extensor tendonof origin; 12C, cranial ligament of fibular head; 13C, fibula; 14C,tibia; 15C, os femoris.

A medial view of the right stifle showing associated ligaments andstructures is shown in FIG. 4. The following features are identified:1D, os femoris; 2D, medial femoropatellar ligament; 3D, sesamoid; 4D,medial collateral ligament; 5D, popliteus tendon of origin; 6D, cranialligament of the fibular head; 7D, fibula; 8D, tibia; 9D, tibial crest;10D, tibial tuberosity; 11D, patellar ligament; 12D, medial meniscus;13D, patella; 14D, quadriceps muscle group tendon of insertion.

A medial view of the left pelvic limb muscles and associated structuresis shown in FIG. 5. The following features are identified: 1E, cranialsartorius; 2E, caudal sartorius; 3E, cranial tibial; 4E, deep digitalflexor; 5E, tibia; 6E, common calcanean tendon; 7E, superficial digitalflexor; 8E, gastrocnemius; 9E, biceps femoris tendon of insertion; 10E,semitendinosus, 11E, gracilus; 12E, pectineus; 13E, vastus medialis;14E, adductor magnus et brevis; 15E, semimembranosus.

A lateral view of the right pelvic limb muscles and associatedstructures is shown in FIG. 6. The following features are identified:1F, middle gluteal; 2F, tensor fasciae latae; 3F, cranial sartorius; 4F,vastus lateralis; 5F cranial tibial; 6F, gastroenemiius; 7F, superficialdigital flexor; 8F, long digital extensor; 9F, common calcanean tendon;10F, biceps femoris tendon of insertion; 11F, caudal head of bicepsfemoris; 12F, cranial head of biceps femoris; 13F, semitendinosus; 14F,semimembranosus; 15F, superficial gluteal.

The cranial cruciate ligament (CrCL) prevents cranial tibial translationor the tibial forward thrust, limits excessive internal rotation of thetibia and prevents hyper extension of the stifle. During the stancephase (weight bearing phase) of the gait cycle, loading of the stiflejoint leads to a ventrally directed compressive force, and ahorizontally directed force, or a cranial tibial thrust. In an intactstifle, the CrCL resists this force, minimizing any cranial translationof the tibia. In a CrCL deficient stifle, the lack of the stabilizingforce, leads to cranial translation of the tibia during the weightbearing phase of the gait cycle. The translation of the tibia during thestance phase can alter the load distribution within the stifle joint,leading to pain, stiffness and osteoarthritis of the joint.

Common surgical treatment options for cruciate ligament disease areTibial Plateau Levelling Osteotomy (TPLO) and Tibial TuberosityAdvancement (TTA). In a TPLO surgery, illustrated in FIG. 7, asemi-circular cut is made on the dorsal end of the tibia. The tibialarticular surface is then rotated and stabilized using bone plates andscrews. By levelling the tibial plateau, cranial slippage of the tibiaduring the stance phase is prevented. In a TTA surgery, illustrated inFIG. 8, the attachment site of the patellar tendon to the tibia is movedforward by cutting the tibial tuberosity and repositioning it with boneplates and screws.

TPLO and TTA both carry a risk of failure due to poor bone healing afterthe osteotomy, as well as a risk of failure due to fracture of the boneweakened by the osteotomy. Moreover, these surgeries require significantpain management following surgery and entail long recovery times.

SUMMARY OF DISCLOSURE

Exemplary methods disclosed herein comprise selecting at least one ofthe muscles and connective tissues associated with the canine stiflejoint as target tissue for treatment, and displacing the target tissuewithout severing the bones or target tissue, thereby achieving atherapeutic effect. In exemplary embodiments described herein, thetarget tissue is displaced by placing an implant in contact with thetarget tissue and displacing the target tissue to reduce cranial tibialthrust. The implant may be secured to a bone and/or to soft tissues,which may include the target tissue. In a preferred embodiment, thecapsule surrounding the joint is not penetrated. Implants may be securedvariously on medial, lateral, caudal or cranial sides of the femur orthe tibia to displace target connective tissue or muscle comprising atleast one of the quadriceps muscle or tendon, the patellar tendon, thebiceps femoris muscle or tendon, or the semitendinous muscle or tendon.Displacement may be in the caudal or cranial direction relative to thebone on which the implant is placed. The implant may be completelyoutside the capsule surrounding the stifle joint or may be in contactwith the exterior of the capsule.

In one implementation, the present disclosure is directed to a methodfor treating canine cruciate ligament disease. The method includessecuring an implant to one of the canine femur or tibia and reducingcranial tibial thrust by displacing connective tissue or muscle actingon the canine stifle joint with the implant, wherein the displacingcomprises displacing the hamstring muscles caudally.

In another implementation, the present disclosure is directed to amethod for treating canine cruciate ligament disease. The methodincludes securing an implant to one of the canine femur or tibia outsideof the capsule surrounding the stifle joint, positioning a displacementportion of the implant under the hamstring muscles, and displacing thehamstring muscles caudally with the displacement portion to repositionthe hamstring muscles greater than about 2 mm up to about 25 mm beyondthe natural anatomical track of the hamstring muscles.

In yet another implementation, the present disclosure is directed to adevice for treating canine cruciate ligament disease. The deviceincludes an implant configured and dimensioned to be secured to one ofthe canine femur or tibia and to extend under a target tissue, thetarget tissue comprising at least one connective tissue or muscle of thestifle joint including at least the hamstring muscles, to displace thetarget tissue sufficiently to reduce cranial tibial thrust, wherein theimplant comprises a fixation portion configured to be secured to one thebone, and a displacement portion extending from the fixation portion andconfigured to atraumatically contact and displace the hamstring musclescaudally.

In still another implementation, the present disclosure is directed toan implant for treating canine cruciate ligament disease. The implantincludes a fixation portion configured and dimensioned to be secured toa fixation site on one of the canine femur or tibia, a displacementportion configured and dimensioned to extend under and caudally displacethe hamstring muscles from a natural anatomical track, the displacementbeing sufficient to reduce cranial tibial thrust, a bearing surface inthe displacement portion, the bearing surface a smooth surface free ofdiscontinuities to atraumatically engage and displace the hamstringmuscles, and a spanning section extending between the fixation portionand the displacement portion, the spanning section being configured toposition the displacement portion and bearing surface under thehamstring muscles with the fixation portion secured to the fixationsite.

By using the implants of the invention, appropriately sized andpositioned as described herein, displacement of targeted connective andmuscle tissues surrounding the joint is accomplished in order to realignforce vectors and/or alter moment arms loading the joint to achievetherapeutic effects without cutting bone and with minimal cutting of theconnective tissues. Alternative and more specific devices andmethodologies are described in more detail herein below.

BRIEF DESCRIPTION OF DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more exemplary embodiments of the invention. However, itshould be understood that the present invention is not limited to theprecise arrangements and instrumentalities shown in the drawings,wherein:

FIG. 1 is the cranial view of a left canine stifle joint showingligaments and associated structures.

FIG. 2 is the caudal view of a right canine stifle joint showingligaments and associated structures.

FIG. 3 is the lateral view of a right canine stifle joint showingligaments and associated structures.

FIG. 4 is the medial view of a right canine stifle joint showingligaments and associated structures.

FIG. 5 is the medial view of a left canine pelvic limb showing musclesand associated structures.

FIG. 6 is the lateral view of a right canine pelvic limb showing musclesand associated structures.

FIG. 7 is a schematic representation of Tibial Plateau LevellingOsteotomy.

FIG. 8 is a schematic representation of Tibial Tuberosity Advancementosteotomy.

FIG. 9 is a cranial view of a left canine stifle joint illustratingpositioning of an exemplary embodiment of the present invention fortreating cruciate ligament disease.

FIG. 10 is a cranial view of a left canine stifle joint illustratingpositioning of another exemplary embodiment of the present invention fortreating cruciate ligament disease.

FIG. 11 is a medial view of a right canine stifle joint illustratingpositioning of a further exemplary embodiment of the present inventionfor treating cruciate ligament disease.

FIG. 12 is a lateral view of a right canine stifle joint illustratingpositioning of yet another exemplary embodiment of the present inventionfor treating cruciate ligament disease.

FIG. 13 is a medial view of a right canine stifle joint illustratingpositioning of another exemplary embodiment of the present invention fortreating cruciate ligament disease.

FIG. 14 is a medial view of a right canine stifle joint illustratingpositioning of another exemplary embodiment (#600) of the presentinvention for treating cruciate ligament disease.

FIG. 15 is a lateral view of a right canine stifle joint illustratingpositioning of another exemplary embodiment of the present invention fortreating cruciate ligament disease.

FIG. 16 is a caudal view of a right canine stifle joint illustratingpositioning of another exemplary embodiment of the present invention fortreating cruciate ligament disease.

FIG. 17 is a caudal view of a right canine stifle joint illustratingpositioning of another exemplary embodiment of the present invention fortreating cruciate ligament disease.

FIG. 18 is a caudal view of a right canine stifle joint illustratingpositioning of another exemplary embodiment of the present invention fortreating cruciate ligament disease.

FIG. 19 is a cranial view of a left canine stifle joint illustratingpositioning of another exemplary embodiment of the present invention fortreating cruciate ligament disease.

FIG. 20 is a cranial view of a left canine stifle joint illustratingpositioning of another exemplary embodiment of the present invention fortreating cruciate ligament disease.

DETAILED DESCRIPTION

Utilizing embodiments of the present invention, joint conditions thatresult from or exacerbate unbalanced force distribution through thejoint may be addressed by interventional techniques involving aredistribution of forces exerted on the joint without the need forhighly invasive surgeries requiring significant trauma to the joint andassociated muscle and connective tissues. Redistribution of forceswithin the target joint in accordance with embodiments described hereinmay thus provide pain relief or slow down articular cartilagedegeneration or enhance cartilage regeneration.

In some embodiments of the invention, increased forces can beselectively applied to one side of a joint by routing select muscle,tendons, ligaments, and/or other connective tissues (target tissues)around a longer, curved, or more angled path, thus increasing themagnitude, altering the effective direction, and/or changing the momentarm of forces exerted by such muscles or tissues on the joint. This maybe accomplished, for example, by appropriately shaped implants that maybe positioned to displace selected target tissues relativelynon-invasively compared to current surgical techniques for addressingsuch conditions. The amount of displacement of the target tissue may notneed to be large in order to provide a substantial therapeutic effect onthe target joint. Depending upon the nature of the disease and the sizeand geometry of the particular canine joint, displacements of greaterthan about 2 mm up to about 25 mm may be sufficient, with displacementsin the range of about 3 mm to about 20 mm also suitable, or morespecifically about 4-15 mm.

Exemplary embodiments of the invention described herein are particularlydirected to treatment of canine cruciate ligament disease, although theprinciples of the invention may be applied to other canine or humanarticular joints as described in the above identified relatedapplications of the present provisional application, which as statedabove are incorporated by reference herein. In general, it will beappreciated by persons of ordinary skill in the art that specificfeatures described in connection with one exemplary embodiment may beincorporated in other exemplary embodiments unless otherwise noted. Theexemplary embodiments described are thus included to illustrate featuresof the invention, not limit it.

As used herein, “therapeutic effect” means an effect on a treated jointthat reduces forces acting on the articular surfaces, reduces abnormalmotion of the bones during flexion/extension, reduces wear, lessens painor provides another positive outcome for the patient whether across thejoint as a whole or in particular parts of the joint. In the caninestifle joint, therapeutic effect would generally be associated with areduction in cranial tibial thrust. “Therapeutic effect,” however, doesnot imply, and should not be understood as requiring, any specific,quantified outcome other than as stated above.

As used herein, dorsal means directed towards the back, ventral meansdirected towards the belly, medial means directed towards the mid-line,lateral means directed away from the mid-line towards the flank, cranialmeans directed towards the cranium (head) and caudal towards the tail.Proximal refers to the end of a structure nearest a major point ofreference and distal to the end furthest from a point of reference. Thepoint of reference is usually the origin of a structure (such as alimb). Dorsal plane is parallel to the back, transverse plane isperpendicular to the long axis of the body and sagittal plane dividesthe body into right/left parts.

Implants according to embodiments of the present invention may beconfigured and secured in a variety of ways as described below in moredetail with respect to exemplary embodiments. However, in general, andwith reference to implant 100 shown in FIG. 9, prostheses or implantsaccording to embodiments of the invention may comprise a fixationportion 101 configured to be secure to the bone at a specific location,and which may provide means for securing or anchoring the prosthesis,such as holes for bone screws 110, and a displacement portion 103configured and dimensioned to displace the target tissue(s) from apretreatment path as described herein. Other means for securing thefixation portion may include bone ingrowth surfaces, barbs, bone cement,features for fastening sutures or wires, and other devices known in theart for securing implants to bone. The fixation and displacementportions may be separated by a spanning section 102 configured anddimensioned to position the displacement portion with respect to thefixation portion as appropriate to accommodate the anatomical structuresat the location of treatment and fixation. For example, the spanningsection may be configured to avoid tendon attachment sites between thefixation and displacement region. The displacement portion 102 may beprovided with a bearing member for engaging the target tissue, which maybe the same or a different material than the underlying substrate.

Depending on the mechanical load on the implant, and the choice ofmaterial or materials used to fabricate the implant, thickness of thefixation portion. The thickness of the fixation portion of the implantmay be uniform throughout the implant or may vary across the implant.Regions of the fixation portion under higher mechanical load may bethicker than regions under lower mechanical loads. The thickness of thefixation region may also be selected to ensure that the screw-heads usedto fix the implant do not protrude over the surface of the implant.

The spanning section may have thickness similar to that of the fixationportion. Persons of ordinary skill in the art will appreciate that aprincipal consideration for spanning section is sufficient structuralintegrity to maintain the displacement portion at the desired treatmentposition. In the displacement portion, displacement distance andthickness may be considered separately. Displacement distance is thedistance by which the bearing surface of the displacement portiondisplaces the target tissue beyond the natural anatomical track of thetarget tissue, in other words, the displacement of tissue created by theimplant. Depending on the particular geometry of the implant, thethickness of the displacement portion may or may not be related to thedisplacement distance.

In alternative embodiments, components of the prosthesis may be acompliant material such as an elastomer, capsules filled with water,saline, silicone, hydrogels, etc. Embodiments with compliant portionscould be placed in a deflated state and then inflated to the appropriatethickness. Alternatively, bearing members may be filled with otherflowable materials including beads or other particles made of metal,polymer, or foam material, optionally in a liquid medium, which conformto the adjacent bone or tissue surfaces. Thixotropic materials, such ashydrogels derived from hyaluronic acid, change their mechanicalproperties as shear stress is applied to them. An implant filled withsuch materials could be made to change the amount of displacement thatit provides based on the shear stress that it sees from overlying targettissues at various points in the gait cycle. Implants may be coated withmaterials to reduce friction such as hydrophilic coatings orpolytetrafluoroethylene (PTFE) coatings. Additionally or alternatively,the prosthesis may be adjustable to allow the dimensions such asthickness of the prosthesis to be adjusted during surgery or any timeafter surgery.

Rigid or substantially rigid prostheses according to embodiments of theinvention described herein could be made of known bone-compatibleimplant materials such as titanium or stainless steel. Biocompatiblepolymers, ceramics, and other materials may also be used. The bearingsurface of the prostheses should be designed to minimize negativeeffects of movement of the connective tissues across the implantsurface, e.g. comprising a smooth, atraumatic, low-friction material,coating or surface treatment. Such prostheses could be implantedarthroscopically or using a mini-open or open surgical approach.

In various alternative embodiments, the displacement portion and thefixation portion of prostheses according to the invention may be ofunibody construction, or may be formed of two or more parts depending ondesired function. For example, the fixation portion may be stainlesssteel or titanium textured to enhance bony ingrowth and solid screwfixation, while the displacement portion could be made of a differentmaterial, for example, pyrolytic carbon to enhance the ability ofoverlying tissues to slide across the implant, or PTFE, silicone orother low-friction polymer with suitable wear characteristics to providea softer bearing surface. In this regard, the displacement portion maycomprise a separate bearing member with a bearing surface on which thetarget tissue bears. Alternatively the bearing surface may be formed asan integral part of the displacement portion. In further alternatives,the displacement portion could be comprised of a substrate of onematerial with an overlying layer forming the bearing member. Thesubstrate could be either attached to or contiguous with the fixationportion. In other embodiments, the fixation portion of the implant mayhave a relief feature to minimize contact with the underlying bone,thereby minimizing disruption of the periosteal layer.

Generally, the bearing member and/or bearing surface in embodiments ofthe invention will be hard and smooth, made from materials such aspolished pyrolytic carbon, steel, or titanium, or coated or covered witha lubricious material, such as PTFE. However, in embodiments whererelative motion is provided for within the prosthesis itself, such as inexemplary embodiments described herein below, the bearing surface may bedesigned to encourage adhesion and ingrowth of the connective tissueonto this surface. For example, such a surface may be porous, roughened,or configured with openings into which bone or scar tissue may grow toenhance adhesion.

In some embodiments, the implant could be anchored to the underlyingbone with suitable fasteners such as screws. Depending on the locationand surgical need, unicortical screws, bicortical screws, cancellousscrews, cannulated screws, polyaxial screws, screws that lock into theimplant etc. may be used. In some embodiments, the screw holes may belocking threads or other locking features. In other embodiments, thescrews holes may be oriented in different directions to improve thestability of the anchored implant. In alternate embodiments, differenttypes of screws may be used in different regions of the implant. Forexample, cortical screws may be used in the region of the implant incontact with the femoral shaft while cancellous screws may be used inanother part of the implant in contact with femoral condyle. Dependingon patient anatomy and geometry of a specific implant, it may bedesirable to provide supplemental fixation (such as cancellous bonescrews) in the spanning section.

As discussed above, joint pain, joint stiffness or joint osteoarthritismay result from cranial tibial translation caused by cruciate ligamentdisease. By caudally displacing the caudal muscles or tendons like thesemitendinosus, semimembranosus or biceps femoris muscle or tendon, themoment arm of the muscle or tendon as it crosses the joint may beincreased, thereby stabilizing the joint during the gait cycle. Bycranially displacing the cranial muscles or tendons like the quadricepsmuscle or tendon, or patellar tendon, the moment arm of the muscle ortendon as it crosses the joint may be increased, thereby stabilizing thejoint during the gait cycle. Other muscles and tendons around the kneethat contribute to the cranio-caudal stability of the knee may also bedisplaced to achieve a similar therapeutic effect.

In one embodiment, displacement of the target tissue results in thedecrease in the cranial tibial translation or thrust in the targetstifle joint by at least about 0.5 mm, more preferably by at least about1 mm, most preferably by at least about 1.5 mm. Reduction in cranialtranslation as defined here refers to decrease in translation, eithermaximum or average translation, either measured or calculated, during anormal gait cycle, running, jogging or any other physical activity whichresults in mechanical loading of articular cartilage in a stifle joint.

As discussed above, FIG. 9 shows one exemplary embodiment of the presentinvention for cranial displacement of the quadriceps muscle or tendon.Implant 100 is anchored to the medial side of the femur. Fixationportion 101 of the implant is used to anchor the implant, e.g. withscrews 110, and displacement portion 103 displaces the quadriceps muscleor tendon cranially. Spanning section 102 would be configured totransition from fixation portion 101 mostly parallel to the medial sideof the femur to displacement portion 103, which is disposed on a morecranial aspect of the femur so as to displace the quadriceps muscle ortendon cranially.

FIG. 10 shows another exemplary embodiment of the present invention forcranial displacement of the patellar tendon. In this embodiment, implant200 may be anchored to the medial side of the tibia. Fixation portion201 of the implant is used to anchor the implant, e.g. with screws, anddisplacement portion 203 displaces the patellar tendon cranially.Advantageously, the fixation portion is separated from the displacementportion by spanning section 202 so that the fixation portion may beshaped and dimensioned to optimize anchoring, holes 209 for screws maybe more numerous and separated further apart, and the location on thebone for anchoring may be more easily accessed and visualized by thesurgeon. Displacement portion 203 preferably has a convex curvature onits outer tissue-engaging surface (bearing surface), preferably beingcurved at least around an axis generally parallel to the tibial shaft,usually being curved also around an axis perpendicular to the tibialshaft, and more preferably being spherical or partially spherical.Displacement portion 203 is disposed over a more cranial aspect of thetibia so as to be located under the patellar tendon between the tendoninsertion point and the dorsal end of the tibia.

In embodiments of the present invention, implants may be configured suchthat the displacement portion of the implant is separated from thefixation portion of the implant. With the displacement portionpositioned under the target tissue (e.g. patellar tendon), the fixationportion of the implant may be configured to be affixed to the bone at alocation which can securely fix the implant in place, is accessible tothe surgeon, is not covered by the target tissue, and is separated fromtendon insertion points and other anatomical features. The implant mayhave a spanning section configured and dimensioned to bridge thedistance between the fixation portion and the displacement portion. Theimplants may be configured to move the tendon anteriorly or medially oranterior-medially or laterally or antero-laterally. This may beaccomplished by making one side (lateral or medial) of the displacementsurface higher than the other, and/or by forming a track with ridges onone or both sides of the bearing surface to urge the tendon in a lateralor medial direction.

FIG. 11 shows an exemplary embodiment of the present invention forcranial displacement of the patellar tendon. Implant 300 is anchored tothe medial side of the tibia.

FIG. 12 shows an exemplary embodiment of the present invention forcranial displacement of the patellar tendon. Implant 400 is anchored tothe lateral side of the tibia.

FIG. 13 shows an exemplary embodiment of the present invention forcaudal displacement of the hamstring muscles. Implant 500 is anchored tothe medial side of the femur. Implant 500 has a displacement portionconfigured to be located along a caudal aspect of the femur under thehamstring muscle so as to displace the hamstring caudally, that is, awayfrom the femoral shaft.

FIG. 14 shows an exemplary embodiment of the present invention forcaudal displacement of the hamstring muscles. Implant 600 is anchored tothe medial side of the tibia.

FIG. 15 shows an exemplary embodiment of the present invention forcaudal displacement of the hamstring muscles. Implant 700 is anchored tothe lateral side of the femur.

FIG. 16 shows an exemplary embodiment of the present invention forcaudal displacement of the hamstring muscles. Implant 800 is anchored tothe medial side of the femur.

FIG. 17 shows an exemplary embodiment of the present invention forcaudal displacement of the hamstring muscles. Implant 900 is anchored tothe lateral side of the femur.

FIG. 18 shows an exemplary embodiment of the present invention forcaudal displacement of the hamstring muscles. Implant 1000 is anchoredto the medial side of the tibia.

FIG. 19 shows an exemplary embodiment of the present invention forcranial displacement of the patellar tendon. Implant 1100 is anchored tothe lateral side of the tibia.

FIG. 20 shows an exemplary embodiment of the present invention forcranial displacement of the quadriceps muscle or tendon. Implant 1200 isanchored to the lateral side of the femur.

As with other embodiments described herein, the displacement of thetarget tissue can be altered by changing the length, curvature and angleof the spanning section and/or dimensions of the displacement andfixation portions as appropriate for specific canine anatomy.

The spanning sections may also comprise adjustable mechanisms (e.g. apin or hinge) to movably or pivotably alter the orientation or anglebetween the two parts to achieve the appropriate level of tissuedisplacement.

In some embodiments of the present invention, the displacement of theconnective tissue could be adjusted by adjusting the devicepre-operatively, intra-operatively or post-operatively. Devices mayinclude mechanisms that are remotely controlled and/or enable wirelesscommunication to alter the displacement after implantation.Alternatively, the displacement may be adjusted by applying an energyfields (e.g.; magnetic field, electric field, thermal field etc.)transdermally from an external location.

In various adjustable embodiments described above, the adjustmentmechanisms themselves may be radiopaque and/or otherwise discernablefrom the rest of the implant under x-ray in order to enablepost-surgical percutaneous adjustment of the device. Alternatively,target features can be built into the device to locate the adjustmentpoints without having the screws or adjustment means themselvesradiopaque, such as radiopaque rings or markers built into the nearingsurface of the device itself.

The implants described above may be implanted in areas adjacent to thejoint such that the soft tissue is displaced in a region it crosses thejoint. Alternatively, the device could be implanted away from the jointand displace the target soft tissue in a region that it is not crossingthe joint.

In other alternative embodiments, displacement portions of previouslydescribed static implants may be provided with a roller or other dynamicfeature to further reduce wear or trauma to the displaced tissue. Insome embodiments, the inferior surface of the displacement region iselevated off the underlying tissue. The underlying tissue could be boneor soft tissue like tendon, muscle, ligament, bursa, capsule etc.Elevating the inferior surface off the underlying tissue could bebeneficial by minimizing damage to soft tissue, reducing any potentialrestriction to joint motion due to compression of soft tissue etc.

In some embodiments, the displacement region will have a continuousbearing surface which is in contact with the target connective tissue(muscle, tendon, ligament etc.) and is devoid of any discontinuities.Discontinuities would include fixation channels for long-term fixationlike screw holes, holes for sutures etc. as well as fixation channelsfor temporary fixation like holes for Kirschner-wires (K-wires). Thelack of discontinuities in the bearing surface would minimize thepotential for wear or irritation of the target connective tissue. Thebearing surface of the displacement section may be polished, coated ormodified in other ways to minimize wear of the bearing surface and/orwear of the target connective tissue.

In some embodiments, the bearing surface of the displacement regionwhich is in contact with the target connective tissue (muscle, tendon,ligament etc.) may have features that enable adhesion or attachment ofthe target connective tissue to the bearing surface. Attachment of thetarget connective tissue on the implant surface may minimize motion ofthe tissue across the implant surface during joint motion. Thesefeatures would include channels for formation of fibrous tissue from thetarget connective tissue anchoring the connective tissue to thedisplacement surface of the implant.

In some embodiments, the bearing surface of the displacement region mayhave surface features that enable adhesion or attachment of the targetconnective tissue to the bearing surface. These features would includeprojections, microprojections, bumps, ridges, pin-like projections,granular surface etc.

In some embodiments, the inferior surface of the displacement region maybe in contact with the underlying tissue. In other embodiments, part ofthe inferior surface of the displacement section may be in contact withthe underlying tissue.

In some embodiments, the inferior region may have features like channelsfor fibrous or bony tissue ingrowth to enable adhesion or attachment ofthe underlying tissue to the bearing surface. In other embodiments, theinferior region may have features like projections, microprojections,bumps, ridges, pin-like projections, granular surface etc. Attachment ofany soft connective tissue underneath the inferior surface of thedisplacement region may minimize motion of the tissue under the implantduring joint motion. In other embodiments, the inferior surface may havepins for anchoring the implanting into underlying bone.

In some embodiments, the device may be a two-part device with the firstpart (base unit) comprising the fixation section, the spanning sectionand the displacement section, and the second part (bearing unit)configured to attach to the displacement section of the base unit. Inother embodiments the bearing unit may be configured to attach to thespanning section and to cover the displacement section of the base unit.The bearing unit may be configured to minimize tissue wear or to enabletissue adhesion or attachment. In one embodiment, the displacementsection and the bearing unit would have features to attach the twounits.

In some embodiments, the displacement region may have channels to assistin positioning, placement or temporarily anchoring of the implantintra-operatively.

As will be evident to one skilled in the art, the dimensions of theexemplary embodiments above can be altered to address differences injoint size, condyle size, level of the tissue displacement etc. as wellas to enable positioning and securing the implant at the surgical sitewhile minimizing trauma to the surrounding bone, tendons, muscles,ligaments and other anatomical structures.

While the invention has been illustrated by examples in variouscontexts, the devices of the present invention may be used to displaceany of the muscles and connective tissues around the stifle joint toachieve a therapeutic effect. For example, the muscle displaced could bethe popliteus muscle, gastrocnemius muscle, vastus lateralis muscle,vastus medialis muscle and the semimembranosus muscle. Alternatively,the tendon associated with any of the muscles could be displaced.

While the invention has been illustrated by examples in various contextsof treating canine cruciate ligament disease, it will be understood thatthe invention may also have application to treatment of other animalslike cats, horses etc.

Exemplary embodiments have been disclosed above and illustrated in theaccompanying drawings. It will be understood by those skilled in the artthat various changes, omissions and additions may be made to that whichis specifically disclosed herein without departing from the spirit andscope of the present invention.

The invention claimed is:
 1. A method for treating canine cruciateligament disease in a canine stifle joint, comprising: securing animplant to one of a canine femur or a canine tibia; and reducing cranialtibial thrust by displacing connective tissue or muscle acting on thecanine stifle joint with said implant, wherein said displacing comprisesengaging at least a hamstring muscle or tendon with the implant so as todisplace the hamstring muscle or tendon caudally sufficiently to alter aforce exerted by the hamstring muscle or tendon on the stifle joint suchthat cranial tibial translation is reduced wherein the implant comprisesa displacement portion positioned on a caudal aspect of the femur aftersaid securing, and wherein the implant comprises a fixation portionanchored to a lateral or medial side of the femur after said securing.2. The method of claim 1, wherein said engaging comprises thedisplacement portion displacing the hamstring muscle or tendon away froma femoral shaft of the femur.
 3. A method for treating canine cruciateligament disease in a canine stifle joint comprising: securing animplant to one of a canine femur or a canine tibia; and reducing cranialtibial thrust by displacing connective tissue or muscle acting on thecanine stifle joint with said implant, wherein said displacing,comprises engaging at least a hamstring muscle or tendon with theimplant so as to displace the hamstring muscle or tendon caudallysufficiently to alter a force exerted by the hamstring muscle or tendonon the stifle joint such that cranial tibial translation is reducedwherein the implant comprises a displacement portion positioned on acaudal aspect of the femur after said securing, and, wherein the implantcomprises a fixation portion anchored to a lateral or medial side of thetibia after said securing.
 4. The method of claim 3, wherein saidsecuring comprises positioning the implant outside of the capsulesurrounding the canine stifle joint.
 5. The method of claim 3, whereinsaid securing and said reducing are achieved without cutting bone of thefemur or tibia.
 6. The method of claim 3, wherein the displacing isgreater than about 2 mm up to about 25 mm beyond the natural anatomicaltrack of the displaced tissue.
 7. The method of claim 6, wherein saiddisplacing is in a range of about 4-15 mm.
 8. The method of claim 3,wherein further comprising selecting the hamstring muscle or tendon asat least one of a biceps femoris, a semitendinosus, and asemimembranosus.
 9. The method of claim 3, wherein said securingcomprises positioning the implant outside of the capsule surrounding thecanine stifle joint.
 10. The method of claim 3, wherein said securingand said reducing are achieved without cutting bone of the femur ortibia.
 11. The method of claim 3, wherein the displacing is greater thanabout 2 mm up to about 25 mm beyond the natural anatomical track of thedisplaced tissue.
 12. The method of claim 11, wherein said displacing isin a range of about 4-15 mm.
 13. A method for treating a canine stiflejoint, comprising: securing an implant to one of a canine femur or tibiain engagement with at least one hamstring muscle or tendon acting on thecanine stifle joint; and displacing the at least one hamstring muscle ortendon with said implant by said engagement to reduce cranial tibialthrust acting on the canine stifle joint, wherein the canine stiflejoint has a joint capsule, and wherein: said securing comprises fixingthe implant to the canine femur or tibia with at least one bone screwwithout penetrating the joint capsule; and said securing and displacingare performed without cutting the hone to which the implant is secured.14. The method of claim 13, wherein said displacing comprisesrepositioning the at least one hamstring muscle or tendon caudallygreater than about 2 mm up to about 25 mm beyond the natural anatomicaltrack of the hamstring muscle or tendon.